Hybrid Hughes‐Hartogs power allocation algorithms for OFDMA systems

Abstract

This work analyses the discrete solution of Hughes-Hartogs (HH) for the transmission rate maximisation problem with power constraint in the orthogonal frequency division multiplexing access (OFDMA) systems and explores mechanisms to reduce the computational complexity of greedy algorithms. In addition to the solution characterisation, a computational complexity analysis is developed, considering the number of executed operations for running time purpose. Moreover, the authors have compared the system capacity via the throughput obtained with the HH solution, and its variants combined with three complexity reduction mechanisms. These tools consist of an initial allocation bit vector calculated by rounding the results of the water-filling (WF) solution, the multiple subchannels per iteration updating and the adoption of a subchannel grouping procedure. Their findings indicate that the update of multiple subchannels and the subcarriers grouping techniques reduce the number of iterations required for convergence of the original HH, with some throughput degradation. Also, the bit-allocation mechanism based on the WF is deployed as an alternative to overcome the HH solution, increasing the computational complexity.

Joint Power Allocation and Bit-Loading for Multicarrier Systems with Discrete Modulation

“…Using this alternative for subcarrier selection, the complexity of the DCA algorithm reduces to ( log( )) [14] which is the complexity of the ordering operation of N vectors each contains K ordered values. This is the main idea in the HH algorithm and there are some works that confuse it with the DCA algorithm when speaking about its complexity [16,17].…”